This invention relates to the use of indolines, more particularly 5,6-dihydroxyindolines, as an additive for hair dye formulations based on substantive dyes or on oxidation dye precursors of the primary intermediate and secondary intermediate type.
The coloring components in conventional hair dye formulations are generally either substantive dyes or dyes which are formed from oxidation dye precursors of the primary intermediate and secondary intermediate type by oxidation with atmospheric oxygen or with other oxidizing agents (for example H2O2). For use in hair dye formations, the dyes are incorporated in a cosmetic carrier. The substantive dyes used are, for example, nitrophenylenediamine derivatives, anthraquinone derivatives or naphthoquinone derivatives.
The oxidation dyes used typically consist of a combination of a primary intermediate, for example a primary aromatic amine containing another free or substituted hydroxy or amino group in the para position or the ortho position, diaminopyridines, heterocyclic hydrazone derivatives, 4-aminopyrazolone derivatives or tetraaminopyridines, and a secondary intermediate, for example m-phenylenediamines, 3-aminophenols, resorcinols, naphthols, pyrazolones. These intermediates react in a coupling reaction in the presence of atmospheric oxygen or other oxidizing agents to form the actual dyes.
Good hair dye formulations are required above all to satisfy the following requirements. They must form the required color tone with sufficient intensity. In addition, they must be readily absorbed onto human hair without overly staining the scalp. The colors produced must be highly stable to heat, light, shampoos and the chemicals used for permanent waving. Finally, hair dye formulations must be toxicologically and dermatologically safe.
Accordingly, there is a constant need for hair dye formulations having improved toxicological and performance properties, more particularly in regard to the fastness of the hair colors produced.
It has now surprisingly been found that it is possible to improve the coloring properties of conventional hair dye formulations both of the primary and secondary intermediate type and also those based on substantive dyes.
Hair colors distinctly superior to the colors obtained with known hair dye formulations in regard to intensity and fastness can be obtained by using only small quantities of indolines corresponding to formula I: 
in which R1, R2, R3, R4 and R5 independently of one another represent hydrogen or C1-4 alkyl groups, or R4 and R5 together with the oxygen atoms to which they are attached represent a C1-4 alkylenedioxy group, or salts thereof as an additive for hair dye formulations containing typical substantive dyes or in hair dye formulations containing oxidation dye precursors of the primary intermediate and secondary intermediate type.
By virtue of the chemical similarity between the indolines of formula I used in accordance with the invention and the basic units of the natural melanin dye present in the hair, the indoline-containing hair dye formulations can also be expected to show favorable toxicological and dermatological behavior.
5,6-Dimethoxyindoline and 5,6-dihydroxyindoline are known from the literature. Their production is described, for example, in J. Chem. Soc. (C), 1967, pages 1424 to 1427. The alkyl-substituted indolines corresponding to formula I can be similarly prepared from the correspondingly substituted 5,6-dihydroxyindoles or alkoxyindoles by catalytic hydrogenation. Another process for the production of 5,6-dihydroxyindolines from 5,6-dimethoxyindoles by reduction with sodium cyanoborohydride and elimination of the methoxy groups in concentrated hydrochloric acid is described in Journal of Medicinal Chemistry, 1978, Vol. 21, No. 6, page 553.
Indolines corresponding to formula I, in which one of the substituents R1, R2 and R3 is a methyl group and the others are hydrogen atoms, are preferred, the parent compound 5,6-dihydroxyindoline being most particularly preferred.
The indolines to be used in accordance with the invention or salts thereof are added on the one hand to hair dye formulations containing oxidation dye precursors of the primary intermediate and secondary intermediate type, a three-component system consisting of typical primary intermediate, typical secondary intermediate and the indoline derivative being formed. However, there is no need to use only one secondary intermediate and one primary intermediate; rather, mixtures of typical secondary intermediates and mixtures of typical primary intermediates may also be used instead of the individual components. On the other hand, the indolines or salts thereof are added to hair dye formulations containing typical substantive dyes.
The indolines corresponding to formula I to be used in accordance with the invention may be used in free form or in the form of their salts, preferably hydrochlorides, hydrobromides, sulfates, phosphates, acetates, propionates, lactates or citrates.
The present invention also relates to hair dye formulations containing indolines corresponding to formula I or salts thereof and typical primary intermediates and typical secondary intermediates in a carrier and to hair dye formulations containing indolines corresponding to formula I or salts thereof and typical substantive dyes in a carrier.
The indolines corresponding to formula I modify the colors obtained with the conventional hair dye systems mentioned above to the extent that depth of color and fastness are both distinctly improved.
Suitable typical primary and secondary intermediates are any of the known compounds, for example resorcinol, 2-methyl resorcinol, xcex1-naphthol, 1,5-dihydroxynaphthalene, 3-aminophenol, p-amino-o-cresol, 2-chloro-3-amino-6-methylphenol, 2,4-dichloro-3-aminophenol, 1,3-bis-(2,4-diaminophenoxy)-propane, 1-phenyl-3-methyl-5-pyrazolone and 1-phenyl-3-amino-5-pyrazolone as secondary intermediates and p-phenylenediamine, p-tolylenediamine, 2-chloro-p-phenyldiamine, N-methyl-p-phenylenediamine and p-aminophenol, for example, as primary intermediates.
Similarly, the typical substantive dye used may be selected from any of the compounds known for this purpose, for example 2-nitro-p-phenylenediamine, 6-chloro-4-nitro-2-aminophenol, 2-amino-4,6-dinitrophenol, 1-(xcex2-hydroxyethyl)-amino-2-nitro-4-bis-(xcex2-hydroxyethyl)-aminobenzene, 1-(xcex2-hydroxyethyl)-amino-2-nitro-4-aminobenzene, 1-(xcex2-hydroxyethyl)-amino-2-nitrobenzene, 1,4-diamino-5-nitroanthraquinone, 1,4-diaminoanthraquinone, 1,4,5,8-tetraaminoanthraquinone, 1-amino-4-methylaminoanthraquinone.
The primary intermediate and the secondary intermediate are each present in the oxidation hair dye in quantities of 0.05 to 5% by weight and preferably in quantities of 0.1 to 2% by weight, based on the hair dye formulation as a whole. Substantive dyes are present in the formulations based on substantive dyes in a quantity of 0.05 to 5% by weight and preferably in a quantity of 0.1 to 2% by weight, based on the hair dye preparation as a whole. The indolines corresponding to formula I are added in quantities of 0.05 to 5% by weight and preferably in quantities of 0.05 to 2% by weight, based on the hair dye formulation as a whole.
To produce the hair dye formulations according to the invention, the substantive dyes or the oxidation dye precursors of the secondary intermediate and primary intermediate type are incorporated in a suitable cosmetic carrier. Suitable cosmetic carriers are, for example, creams, emulsions, gels or even surfactant-containing foaming solutions, for example shampoos, foam aerosols or other preparations suitable for application to the hair.
Typical constituents of such cosmetic preparations are, for example,
wetting agents and emulsifiers, such as anionic, nonionic or ampholytic surfactants, for example fatty alcohol sulfates, alkanesulfonates, xcex1-olefin sulfonates, fatty alcohol polyglycol ether sulfates, ethylene oxide adducts with fatty alcohols, with fatty acids, with alkylphenols, with sorbitan fatty acid esters, with fatty acid partial glycerides and with fatty acid alkanolamides,
thickeners such as, for example, fatty alcohols, fatty acids, paraffin oils, fatty acid esters and other fatty components in emulsified form,
water-soluble polymeric thickeners such as, for example, methyl or hydroxyethyl cellulose, starch, vegetable gums, water-soluble synthetic polymers, water-soluble biopolymers (for example xanthan gum),
hair-care additives such as, for example, water-soluble cationic polymers, protein derivatives, pantothenic acid, vitamins, plant extracts, cholesterol and sugars,
electrolyte and buffer salts, pH regulators, complexing agents and perfume oils,
reducing agents for stabilizing the dye, for example sodium sulfite or ascorbic acid.
To produce the hair dye formulations according to the invention, the constituents of the cosmetic carrier are incorporated in the usual quantities for this purpose. For example, emulsifiers are used in concentrations of 0.5 to 30% by weight, while thickeners are used in concentrations of 0.1 to 25% by weight, based on the hair dye formulation as a whole.
A particularly suitable carrier is an oil-in-water emulsion containing 1 to 25% by weight of a fatty component and 0.5 to 30% by weight of an emulsifier from the group of anionic, nonionic, ampholytic or zwitterionic surfactants. If the indolines to be used in accordance with the invention are used as an additive for hair dye formulations of the primary intermediate and secondary intermediate type, the primary intermediate and secondary intermediate are each incorporated in the carrier in quantities of 0.05 to 5% by weight and preferably in quantities of 0.1 to 2% by weight, based on the hair dye formulation as a whole, while the indolines corresponding to formula I are incorporated in the carrier in quantities of 0.05 to 5% by weight and preferably in quantities of 0.05 to 2% by weight, based on the hair dye formulation as a whole.
Basically, the hair color may be oxidatively developed with atmospheric oxygen. However, it is preferred to use a chemical oxidizing agent, particularly when the hair is to be lightened as well as colored. Suitable oxidizing agents are, in particular, hydrogen peroxide or adducts thereof with urea, melamine or sodium borate and mixtures of such hydrogen peroxide adducts with potassium peroxydisulfate.
The hair dye formulations according to the invention may be used in a mildly acidic, neutral or alkaline medium, irrespective of their cosmetic presentation, for example as a cream, gel or shampoo. The hair dye formulations are preferably used at a pH in the range from 6 to 10 and at a temperature in the range from 15xc2x0 C. to 40xc2x0 C. After a contact time of around 30 minutes, the hair dye formulation is removed from the hair to be dyed by rinsing. The hair is then washed with a mild shampoo and dried. There is no need to wash the hair with a shampoo in cases where a carrier of high surfactant content, for example a dye shampoo, has been used.
The following Examples are intended to illustrate the invention without limiting it in any way.